Guidewires are frequently used to advance intraluminal devices such as stent delivery catheters, dilatation catheters or atherectomy catheters to a desired location within the vasculature. Such procedures typically involve the percutaneous introduction of an interventional device into the lumen of an artery or vein through a catheter or other delivery device.
One specific application guidewires are employed is the placement of a therapeutic device in a patient's vascular system to perform percutaneous transluminal coronary angioplasty (PTCA). In a typical PTCA procedure, a guidewire is introduced through a guide catheter and is advanced through the vasculature to a point distal a lesion. Once the guidewire is in position, a dilatation catheter having an inflatable balloon is advanced along the wire and positioned across the lesion to be dilated. The balloon is then inflated to a predetermined size, causing the lesion to become dislodged from the vessel walls. To prevent the vessel from subsequently reclosing upon removal of the device, or to prevent restenosis from developing over time, a stent can be advanced over the guidewire and placed across the site of the lesion.
During such procedures, it is not uncommon for embolic material such as atherosclerotic plaque to become dislodged from the wall of the artery or vessel, and flow downstream. To collect this dislodged material, an embolic protection filter can be used. These devices are typically placed on a distal section of a guidewire, and are mechanically actuated by struts that self-deploy within the vessel. A mesh screen attached to the device expands in a radial direction to collect the embolic material dislodged during the procedure.
Placement of embolic protection filters is generally accomplished in one of two ways. In one technique, the filter is directly attached to a distal portion of the guidewire prior to insertion in the body. The guidewire and accompanying filter are then inserted through a guide catheter and are placed at a desired location within the patient. Once in position, the guidewire can be used to slide the therapeutic device (e.g. an angioplasty catheter) to perform the procedure. In an alternative technique, a guidewire having a distal stop is first inserted into the patient, and then advanced to a desired location within the vessel. Once in position, the embolic protection filter and therapeutic device are then advanced along the guidewire to a site where the filter can subsequently capture the embolic debris.
Depending on the particular procedure to be performed, it may become necessary to advance multiple intravascular devices along the guidewire throughout the course of treatment. For example, in PTCA, it is not uncommon to exchange an occluded embolic protection filter with a new embolic protection filter should the filter mesh become saturated with embolic debris. When such an exchange is necessary, the movement of the filter and/or therapeutic device along the guidewire may cause the position of the guidewire to shift within the vessel, requiring the physician to re-position the guidewire. Furthermore, since relatively large outer diameters are often required to accommodate the filter and supporting catheter, the steering and tracking characteristics generally preferred in more conventional guidewires are often sacrificed in guidewires adapted for use with embolic protection devices.